1. Field of the Invention
The present invention relates to the field of electric vehicle batteries, and in particular, to a battery internal short-circuit detection method based on battery cell balancing.
2. Description of Related Art
Due to problems in manufacturing processes and use pattern, a battery usually slowly develops an “internal short-circuit.” A manifestation of an internal short-circuit is that although a battery is disconnected, there is still a local or global internal current loop within the battery cell. This loop causes internal circulation of current, thereby consuming battery energy and producing heat. In an extreme situation, a battery temperature may increase sharply, causing a potential hazard.
There are mainly two industrial methods for determining whether a battery has developed internal short-circuit. In one method, a magnitude of a leak current is deduced from change of a charge capacity of a battery after the battery is disconnected. This method, however, has the drawback of not being capable of effectively taking into account a resistance change inside a battery and its accuracy is easily impacted by change of an external temperature and a degree of a battery charge. The other method involves tracking for a sudden change of a battery terminal voltage when the battery is being charged. While this method can effectively identify a local short-circuit, it cannot track a slowly-developing internal short-circuit and is only applicable during charging of the battery.
In U.S. Patent Pub. No. 2014/0266229, an external voltage is applied to each battery cell of a battery pack to be tested for internal short-circuit. An internal short-circuit is determined by means of (externally additional) current measurement. However, this method requires separating a battery pack and applying a voltage to the battery cells from the outside, which is not convenient to operate and can easily result in damages to the battery.